TS-790A Satellite Communications Addendum The information in paragraph 4-9 of the TS-790A Instruction Manual has been revised to explain the satellite operating procedures. Satellite communications utilize numerous frequencies and modes in a pre assigned band plan. Transponders are used to control the contact. For example, part of the band plan of OSCAR 13 utilizes a frequency arrangement known as mode B. In this mode, you would transmit to the satellite (uplink) in the set frequency range of 435.425 -435.575 MHz. Your signal will be be processed by the transponder and re-transmitted back to earth (downlink) in the frequency range of 145.975 - 145.825 MHz. The TS-790A is capable of allowing the uplink and downlink frequencies to track simutaneously by storing the sum of the two frequencies in memory. Memory channels 0-2 are programmed by the factory for Fo-12 and OSCAR 10. The remaining memories are user programmable. To operate the TS-790A in the satellite mode, proceed as follows. Entering Data Determine the uplink and downlink frequencies of the satellite you are tracking. Add the two frequencies together. The sum can now be placed in memory as follows: 1. Press the F key and then the SAT key. Note: This function is inoperative when SUB is selected. 2. Rotate the Tuning knowb to select the desired satellite memory channel. 3. Press the ENT key and then enter the frequency using the numeric keypad. The frequency will be automatically stored after the seventh digit has been entered. Recalling Data The satellite memory channels can be recalled in the following manner. 1. Press the F key and then the SAT key. Note: This function is inoperative when SUB is selected. 2. Rotate the TUNING knob to select the desired satellite memory channel. 3. Press the SAT key to recall the initial mode setting. Operating Procedure: 1. Recall the desired satellite memory channel as described above. 2. Select the SUB function. 3. Use the TUNING knob to select the desired downlink (receive) frequency. 4. Press the SAT key. The MAIN display will shift to the correct uplink frequency. 5. Each time you change the SUB frequency, press the SAT key twice in order to update the MAIN display. The first time the SAT key is pressed, the transceiver goes out of the satellite mode. The second time it is pressed, the transceiver goes back into the satellite mode and updates the MAIN display. An alternative method is to press and hold the SAT key when going into the satellite mode. While the key is held, the TUNING knob can be rotated and both displays will track simultaneously. Note: In step 2, the SUB key was pressed to allow the TUNING knoob to control the downlink (receive) frequency. If the MAIN key is pressed, the tuning knob will control the uplink (transmit) frequency. ADAPTING THE KENWOOD TS-790A FOR USE WITH THE PACCOMM MC-NB96 G3RUH MODEM 12-26-91 The Kenwood TS-790A makes a wonderful 9600 BPS Packet Radio Transceiver as it has an excellent front end, powerful transmitter, and 144,440, and 1.2 GHZ coverage. The CFW-455F filter inside is not too narrow despite what you may have read and coupled with the low noise front end of the rig enables the G3RUH modem to reliably decode valid data that barely moves the S-meter. The modification discribed below is simple, reversible, and does not impair normal operation or the appearance of the transceiver. This is a "no holes" modification as it allows the G3RUH modem to be connected to ACC 4 jack on the rear panel. Place the TS-790A upside down on a soft clean surface so as not to mar the cabinet. Remove the bottom cover to expose the IF. Board. With the front panel facing you the work area is the upper left quarter of the IF board. Identify pin 9 of IC8 (MC3357P). There are two of these chips on the IF board but only the main demodulator IC is in the work area. RX audio to the modem will be derived from this point. Next locate J31 a two pin connector near D81 and X2 (10.965 OSC). TX audio from the modem will be supplied to the hot lead on J31. Note the large aluminum heat sink that spans across the IF board near the rear of the chassis. A round lug will be mounted on it near the rear of ACC 4 jack. Wire an eight pin din plug. Use shielded cable for TX and RX audio. No traces on the IF board need to be cut. Pins 3 and 5 of ACC 4 are not connected to anything as the radio comes from the factory. Make sure the Din plug fits the jack properly before wiring it. PIN 2 - ground PIN 3 - TX audio from G3RUH PIN 5 - RX audio to G3RUH PIN 8 - PTT Prepare two six inch lenghts of RG-174. Prepare one end of each cable so that the shield will reach the ground lug mounted on the large aluminum heat sink. The cables will be routed over the top of the heat sink and will not be crushed when the bottom cover is reinstalled as there is adequate clearance. Solder the center conductor of one cable to pin 3 on the rear of ACC 4 (verify with ohm meter). Solder the center conductor of the other cable to pin 5 on the rear of ACC4 (verify with ohm meter). Dress the cable connected to ACC 4 pin 5 over to IC8 pin 9. Cut to size and solder (be careful- use minimum heat and thin solder). The exposed shield is discarded and heat shrink tubing placed over the end to prevent any shorts that would otherwise occur from having exposed strands of the shield touching something. Dress the other cable connected to pin 3 of ACC 4 to J31 and cut to size. Prepare the end in the same manner as the other cable. Solder the center conductor to pin 2 of J31. This is accomplished by cutting the lead going to pin 2 about 1/2 inch back, stripping the insulation back 1/8 inch on the two ends, and then joining the center conductor of the cable going to pin 3 of ACC 4 and soldering the three exposed ends together. Use heat shrink tubing to cover the solder joint. NOTE that the banded end of D81 is not the cathode of the varactor diode ! There is no need to insert any additional capacitance in series with J31 pin 2. The shields are not connected at both ends of the RG-174 cables in order to prevent ground loops. The Aluminum heat sink was used as ground as no other ground was available that was close to ACC 4. Your sight may be better than mind and you may find one. Adjust VR-1 on the MC-NB96 board for 75 mv p-p as measured on pin 2 of J31. This will give a good initial setting for injected transmit audio level. This completes the modification. 9600 BPS Packet can now be enjoyed on each of the bands installed in your TS-790A. For non-packet operation either unplug the modem from ACC 4 or turn off power to the modem. For 9600 packet operation unplug the mic and turn the mic gain to minimum. Thanks to Frank Anderson, W7ZTA and Jeff Angus, WA6FWI for their help. Please report any errors or suggestions to: Mike Hooper KF6PU @ WB6YMH.#SOCA From : WB5UUK @ N5LKJ.TX.USA.NOAM To : N5EM Date : 911204/0210 Msgid : PN 11593@N5LKJ, 10690@KA5KTH $11593_N5LKJ Subject : TS-790 MOD 2 Path : N5LKJ TS-790 & 9600 Baud Operation (Rev 2) ---------------------------- These notes were partly taken from James Miller, G3RUH notification for FT736R and the article of my good friend Sueo Asato, JA6FTL. These mods are working very well with 9600 bps UO-14 and CBBS operation currently used at my site. Please refer to G3RUH's notification for FT736R for more detail. RX/TX mod suitablity remains same as his notes. TS-790 ; FM Direct from Discriminator ------------------------------------- Detected and amplified/buffered FM direct from the receiver discriminator is available from Pin-9 IC1 (Sub) or IC8 (Main). I use IC1 (Sub) for reception. TS-790 ; Direct varactor FM Modulation -------------------------------------- Inject your TX audio at the cathode side of diode D81 with a 1K ohm register in series. You can find D81 near Q73 in your IF UNIT diagram. Misc ; ------ It takes a bit hard work for very small and jungle PCB. Use tiny tools. Carefully adjust the TX audio level by VR1 of the modem, it's rather low. You would probablly need some local friend to do this adjustment, asking him to tell you his TNC's DCD LED stays steady (no flicker). de Kohjin Yamada, JR1EDE @ JR1EDE.11.JPN.AS ----- End of message 10690 from WB5UUK @ N5LKJ.TX.USA.NOAM ----- From : WB5UUK @ N5LKJ.TX.USA.NOAM To : N5EM Date : 911204/0205 Msgid : PN 11592@N5LKJ, 10689@KA5KTH $11592_N5LKJ Subject : TS-790 MOD Path : N5LKJ TS-790 with serial frequency control ~~~~~~~~~~~~~~~~~~ by Kohjin Yamada, JR1EDE 3 Jun'90 This note is the summary of our discussion made among W9FMW, JA6FTL andmyself. The first report has been brought by WB0KSL expressing TS-790 has audio drops at the frequency change command in it's serial control. JA6FTL confirmed the data loss at the product detecter on his scope too. These are as terrible as if we use KCT Tuner in it's serial control option. Kenwood replied to my inquiry "It is made as so to prevent the noise of PLL, about 100m sec mute is created". Kenwood suggests the modification as below but it should be made on user's responsibility. This should be solved in their next products, I strongly told them. JA6FTL and I confirmed that it now works perfectly on FO-20's actual test and uSATs too with the following modification. Kenwood suggestion; (Refer to IF DIAGRAM) ~~~~~~~~~~ You could disable the mute function by following methods, both or item 2 only. 1) Delete D20 or R191 (for SUB audio) As far as you would use the rear data port (ACC2), it's *NOT* necessary to do this, although you would still have the audio drop at the sound of loud speaker. Of cource, you should do this modification when you would hook up the audio data from Microphone Plug. 2) Put a jumper between Q4 collector and emitter (for SUB RF Block) This modification is a *MUST*. You can do this by several ways but the above is most easy. The following discussion might help you a bit; (partly eddited by me) I wrote to W9FMW; >Cut the line between Q4 Collector and R15 (470 orhm) and Ground the end of >R15. JA6FTL made the mod removing Q4 entirelly and grounding the end of R15. >Q4 located the left of Q5, they are located roughly oposite side of L2, L3. >JA6FTL says the modification needs a magnifying glass, Hi. There is 1 Reply. #: 18154 S5/Amateur Satellites 01-Jun-90 09:08:20 Sb: #18148-TS790 mod for KCT Fm: Sueo Asato JA6FTL 71701,251 To: Kohjin Yamada, JR1EDE 76662,111 Here is additional info. to the modification. Yes..... Need magnifying glass (I am not farsighted nor shortsighted Hi.) This modification is to disable the blocking line for IF amp. Audio muting function remains unchanged, but it is no problem to use rear data port. (Audio muting circuit consists of D20 and Q12) 1.Put the frontside toward you and remove the bottom cover of 790. 2.remove the 13 screws that fix IF board. Lift over up the board toward you. 3.Q5 and Q4 are located just opposite side of L2 and L3. Chip Q5(printed "V11") has 4 solderd legs, and it's located next to R15 (470 ohm surface mount resistor, printed as "471"). Q4 is located just beside R15 and has 3 legs. ----- End of message 10689 from WB5UUK @ N5LKJ.TX.USA.NOAM -----